The storage of materials, including petroleum products and waste materials, in the upstream petroleum industry is dependent on primary containment devices, such as underground and aboveground storage tanks. Such tanks typically include secondary containment measures, which are required in some jurisdictions.
In Alberta, a single-walled above-ground storage tank must have secondary containment consisting of a dike with an impervious liner. However, the regulations permit the use of double-walled above-ground storage tanks (“DW ASTs”) as an alternative to single-walled above-ground tanks and a secondary containment system. However, it has been found that DW ASTs are typically configured with manways and piping through the walls of the tanks. A majority of spills or releases from tanks are the result of operational issues such as overfilling, leaks and drips from valves and fittings, and spillage associated with fluid transfer. These releases are not being contained by the double-wall interstitial space.
The use of an internal containment chamber within single walled tanks is known. Applicant's CA Patent No. 2,196,842 and U.S. Pat. No. 5,960,826 disclose the use of such containment chambers to contain spills and overflows from various valves used in these tanks.